Methods for terminating fiber bundles by means of a core end sleeve are already known. In practice, the bundle of optical fibers is usually inserted into a metal or plastic end sleeve and fixed by crimping or adhesive bonding. The end surface of the fiber bundle is usually ground and polished in order to achieve the lowest possible coupling loss. The minimum possible coupling loss for the coupling of light is realized by the densest possible arrangement of the fibers of 0.4 dB, plus the losses with the coupling in each optical fiber core by the surrounding fiber of 0.4 dB, plus a reflection loss at the interface, which is about 0.2 dB.
The optical fibers can be produced both from plastic and glass. The fibers generally consist of an optical core surrounded by sheathing made of a material with a low index of refraction, which makes it possible to achieve total reflection between the core and the sheathing.
To reduce the coupling loss still further, it is likewise known that the fiber bundles can be heated, so that the cross section of the fibers assumes a hexagonal shape, so that instead of circle packing, hexagonal dense packing is obtained. This further increases the proportion of the optical core in the light exit surface.
A disadvantage of the previously known methods is that they are very expensive and therefore are of limited suitability for applications with high cost pressure, for example, the automobile sector.
In addition, the termination of fiber bundles in places that are poorly accessible, for example, in repair work in a vehicle itself, is scarcely possible.